In these years, there is proposed an MEMS (Micro Electro Mechanical System) sensor for a flow sensor, in which the response speed is faster than that of a coil sensor. The MEMS sensor is generally fabricated in this manner, in which a heater or a temperature sensor is formed on a semiconductor substrate made of silicon or the like by fine patterning used in the fabrication processes for semiconductor devices. However, since the MEMS sensor thus fabricated is corroded with halogen gases, it is difficult that the MEMS sensor is used in the semiconductor fabrication processes in which halogen gases are often used. Thus, an MEMS sensor usable in corrosive halogen gases is conventionally proposed.
In the case where the MEMS sensor is used in corrosive halogen gases, it is necessary that the MEMS sensor have corrosion resistance and toxic halogen gases be prevented from leaking into surroundings by enhancing sealing properties between members forming the passages of the MEMS sensor. However, in the conventional technique, there is no disclosure in terms of enhancing sealing properties in order to prevent halogen gases from leaking into surroundings.